Methyl substituents, directive electronic influence

The electronic influence on the donor ability of the monomers as well as the acceptor behavior of the corresponding cation has been characterized by variation of the para-substituents of the styrenes. More detailed assertions can be expected when one varies the structure directly on the double bond by substitution at a- and P-position. A suprisingly good correlation appears between the energetic level of the HOMO and energy of theCT-absorption of the complexes with TCNE (ECT = 20.8 5.55x(HOMO) r = 0.80 n = 12) for styrenes, both with and without a methyl substituent at a- and p-position ... 

In nitration, an electrophilic aromatic substitution, the electrophile is a nitronium cation. It attacks the benzene ring in the place of the highest electron density. In o-fluorotoluene, there are several positions of high electron density ortho and para with respect to the methyl group, and ortho and para with respect to fluorine. Both substituents, methyl and fluorine, direct the entering electrophile to the activated positions. Whose influence is stronger, that of the methyl group, or that of fluorine ... 

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